I had a 3GS but got the iPhone 4. I ended up jailbreaking and unlocking the 3GS and sending it to my brother to use overseas. Everything's been fine since he got it until just recently. He went to bed and it worked fine. He got the next morning and his wifi was on (he always keeps it off) and he can't download anything from Cydia and he has the "Sim not recognized" message. Also his SBSettings and Winterboard are GONE. He hasn't updated because Cydia is still there. Anyone ever hear of this happening? It's almost as if his jailbreak and unlock just disappeared.